Sam Tobin-Hochstadt wrote:
On Sat, May 25, 2013 at 1:30 PM, Brendan Eich<[email protected]> wrote:
Sam Tobin-Hochstadt wrote:
In the meeting, there were (a) people advocating for styles of
programming along the lines that you (Tab) have put forward, like me,
(b) people advocating for Q-style programming, like Mark, Yehuda, and
Tom, and (c) genuine concern about the complexity budget of the
promise API, expressed most by Luke Hoban, but felt by all of us. Were
it not for this last concern, I think AP2 would have seemed more
attractive. But since the set of methods available on Promises
themselves is the most visible part of the API, and AP2 doubles its
size, that told heavily against AP2.
AP2 from Mark's slides:
AP2 (Based on Tab’s latest)
• Q.fulfill // lifting
• Q() // autolifting, resolve
• p.then // deep flattening
• p.flatMap // “chain”
AP3, next slide:
AP3
• Q.fulfill // lifting
• Q() // autolifting, resolve
• p.then // deep flattening of returned value
There's no doubling, just 4 methods instead of 3.
This is twice as many methods on promises themselves: `then` vs `then`
and `chain`.
Oh, *methods* :-P.
I'm an FPer at heart, can you tell?
Many more people will consume the promise datatype than
produce it, which mean that this does double the methods that
consumers need to know about.
Either they need to know about one method and the {value: x} hackaround,
which is needed sometimes; or they need to know about two methods, then
and chain. Which is worse? You could argue the {value: x} hackaround is
rarely needed, but the same argument can sell chain too. I just don't
see how bean-counting is the right way to assess here.
The problem {value: x} solves is real, no one dismisses it. In arguing
about how to enable developers to solve it, we should count all the
beans and try to assign weights to them. My weighted counting favors a
second method over a manual wrapping pattern. Tab made this point
already in arguing that then + chain is not a union of designs, any more
than then + {value: x} is unioning in the bad committee-designed sense.
From everything you wrote, though, it sounds like TC39 people just
bean-counted methods. Boo...
/be
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